Biomedical subjects

Stephan Schwarz

Publications and source records attributed to Stephan Schwarz.

8 recordsLinked to original sources

PubMed2005

Simultaneous detection of HER2/neu gene amplification and protein overexpression in paraffin-embedded breast cancer.

The determination of HER2/neu status in breast carcinomas has become essential for the selection of breast cancer patients for Herceptin therapy. Herceptin treatment is used in patients with metastatic breast carcinoma with HER2/neu protein overexpression detected by immunohistochemistry (IHC) or gene amplification analysed by fluorescence in situ hybridization (FISH). A multiparametric fluorescent approach based on the simultaneous detection of HER2/neu gene amplification and protein expression was established to increase the accuracy, and to improve the reproducibility, of HER2/neu diagnostics. Based on four paraffin-embedded breast cancer cell lines, a combined fluorescent immunostaining (FIHC) and FISH method was developed by using the PathVysion HER2 DNA Probe Kit (VYSIS) and the polyclonal antibody from the HercepTest (DAKO). Diagnostic applicability was documented on 215 formalin-fixed primary breast carcinomas. Criteria for immunofluorescence quantification were chosen by analogy with the FDA-approved HercepTest scoring, ranging from 0 to 3+. There was 97.7% concordance between conventional IHC and fluorescence IHC. The FISH data resulting from the multiparametric approach did not differ from conventional FISH. Breast carcinomas with HER2/neu protein overexpression and simultaneous gene amplification were detected with 100% sensitivity. In addition, five of the 215 cases (2.3%) had HER2/neu gene amplification without protein overexpression. The main advantage of this novel approach is that polysomy, aneuploidy, gene amplification, and protein content can be analysed simultaneously in the same cell.

Adult↗

PubMed2004

High frequency of functionally active Melan-a-specific T cells in a patient with progressive immunoproteasome-deficient melanoma.

Tumor-reactive T cells play an important role in cancer immunosurveillance. Applying the multimer technology, we report here an unexpected high frequency of Melan-A-specific CTLs in a melanoma patient with progressive lymph node metastases, consisting of 18 and 12.8% of total peripheral blood and tumor-infiltrating CD8+ T cells, respectively. Melan-A-specific CTLs revealed a high cytolytic activity against allogeneic Melan-A-expressing target cells but failed to kill the autologous tumor cells. Loading of the tumor cells with Melan-A peptide reversed the resistance to killing, suggesting impaired function of the MHC class I antigen processing and presentation pathway. Mutations of the coding region of the HLA-A2 binding Melan-A26-35 peptide or down-regulation of the MHC class I heavy chain, the antigenic peptide TAP, and tapasin could be excluded. However, PCR and immunohistochemical analysis revealed a deficiency of the immunoproteasomes low molecular weight protein 2 and low molecular weight protein 7 in the primary tumor cells, which affects the quantity and quality of generated T-cell epitopes and might explain the resistance to killing. This is supported by our data, demonstrating that the resistance to killing can be partially reversed by pre-exposure of the tumor cells to IFN-gamma, which is known to induce the immunoproteasomes. Overall, this is the first report of an extremely high frequency of tumor-specific CTLs that exhibit competent T-cell-effector functions but fail to lyse the autologous tumor cells. Immunotherapeutic approaches should not only focus on the induction of a robust antitumor immune response, but should also have to target tumor immune escape mechanisms.

Antigens, Neoplasm↗

PubMed2003

Correlating genetic aberrations with World Health Organization-defined histology and stage across the spectrum of thymomas.

Thymomas are thymic epithelial tumors. Because most of them are rich in nonneoplastic T-cells, recurrent genetic aberrations have been reported only in the rare, lymphocyte-poor WHO types A, B3, and C. We have now investigated virtually the whole spectrum of thymomas, including the commoner types AB and B2, microdissecting or culturing neoplastic cells from these lymphocyte-rich thymomas and applying 41 microsatellite markers covering 17 loci on 10 chromosomes. In 28 cases, comparative genomic hybridization data were available. Apart from type A, there was striking heterogeneity between thymomas. Allelic imbalances were seen in 87.3% of the 55 cases, and MSI in 9.9%. Losses of heterozygosity (LOHs) were much the commonest aberration. Overall, they were most prevalent at four regions on chromosome 6. Aberrations elsewhere, affecting mainly 8p11.21 and 7p15.3, suggested a cortical footprint because they recurred only in the thymopoietically active type AB and B thymomas. LOHs were also seen at the adenomatous polyposis coli (APC) locus (5q21-22) in subsets of these thymomas, whereas combined LOHs at the APC, retinoblastoma (13q14.3), and p53 (17p13.1) loci were confined to a subset of B3 thymomas that had possibly evolved from APC-hemizygous B2 thymomas by tumor progression; indeed, thymomas combing B2 plus B3 features are common. Notably, some AB and B thymomas shared LOHs despite their nonoverlapping morphology and different clinical behavior. Finally, allelic imbalances at 8p11.21 and 16q22.1 (CDH1) were significantly more frequent in stage IV metastatic thymomas. We conclude that the WHO-defined histological thymoma types generally segregate with characteristic genetic features, type A thymomas being the most homogeneous. Many findings support the view that B2 and B3 thymomas form a continuum, with evidence of tumor progression. However, other findings imply that types A and AB are biologically distinct from the others, any potential invasiveness being severely restricted by a medullary commitment in the precursor cell undergoing neoplastic transformation.

Cells, Cultured↗

PubMed2002

Genetic analysis of de novo CD5+ diffuse large B-cell lymphomas suggests an origin from a somatically mutated CD5+ progenitor B cell.

CD5(+) diffuse large B-cell lymphomas (DLBLs) have recently been described as a particular subgroup of DLBLs. Classical banding and interphase cytogenetic analyses targeting ATM, TP53, and P16(INK4a) genes and the D13S25 locus from 13 CD5(+) DLBLs were compared with 55 CD5(-) DLBLs. Additionally, analysis of somatic mutations of the immunoglobulin heavy chain variable region (IgVH) genes were performed in CD5(+) DLBLs. CD5(+) DLBLs were somatically mutated (7 of 8 cases) and were negative for t(11;14)(q13;q32) and t(14;18)(q32;q21), whereas t(3;14)(q27;q32) was found in only one tumor. Trisomy 3 and gains on chromosomes 16/16p and 18/18q were significantly overrepresented in CD5(+) DLBLs. No ATM deletions were detected. The prevalence of deletions at the D13S25 locus was significantly higher in CD5(+) DLBLs (4 of 12 [33%]) compared with CD5(-) DLBLs (4 of 42 [10%]), as were p16(INK4a) deletions (33% versus 8%). On the basis of these findings, CD5(+) DLBLs are likely to arise from the same progenitor cell as the mutated variant of CD5(+) lymphocytic lymphoma/B-cell chronic lymphocytic leukemia (B-CLL).

B-Lymphocytes↗

PubMed2002

Gastric marginal zone B-cell lymphomas of MALT type develop along 2 distinct pathogenetic pathways.

Low-grade marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) type can transform into high-grade diffuse large B-cell lymphoma (DLBCL). Up to 60% of the MALT lymphomas contain the recently described t(11;18). However, this translocation has not been detected in any DLBCL so far. To elucidate the pathogenesis of these tumors, microsatellite screening of 24 gastric MALT lymphomas was performed and the results were compared with aberrations detected in a previous study on gastric DLBCL. The most frequent aberration, found in 21% of the MALT lymphomas that were exclusively t(11;18)-negative cases, was amplification of the 3q26.2-27 region (harboring the locus of the BCL6 gene). Allelic imbalances in regions 3q26.2-27, 6q23.3-25, 7q31, 11q23-24, and 18q21 were shared by both MALT lymphoma and DLBCL. Loss of heterozygosity in regions 5q21 (APC gene locus), 9p21 (INK4A/ARF), 13q14 (RB), and 17p13 (p53) and allelic imbalances in 2p16, 6p23, and 12p12-13 occurred exclusively in DLBCL. Only one of 10 t(11;18)-positive MALT lymphomas showed an additional clonal abnormality. These tumors thus display features of a clonal proliferation characterized by the presence of the t(11;18). However, they only rarely display secondary aberrations and do not seem to transform into DLBCL. In contrast, t(11;18)-negative MALT lymphomas show numerous allelic imbalances--some of them identical with aberrations seen in DLBCL--suggesting that this group is the source of tumors eventually transforming into high-grade DLBCL.

Adult↗

PubMed2002

VIEWER: a program for visualising, recording, and analysing animal behaviour.

In order to determine the influence of environmental interventions, medical substances, drugs, or diseases on an animal, it is a common to observe the behaviour of the animal in the open field or in other environments. Changes in animal behaviour can be the first indicators for an influence of a substance or an intervention on the organism and certain kinds of behavioural changes can permit speculations about the underlying physiological mechanisms. Behavioural properties which are of interest in this respect are movement parameters such as velocity or direction, activity patterns, spatial distribution and occurrence of several types of standard behaviours of an animal. Observation of simple behaviours such as determining the average activity level can help to detect general changes of the internal state of an animal, while changes in complex behaviours may point to specific influences of a substance or an intervention. Our system 'VIEWER' uses a microcomputer (IBM-compatible PC running WINDOWS 95, WINDOWS 98, WINDOWS NT, or WINDOWS 2000), a low budget framegrabber card (e.g. WinTV, Hauppauge) and a standard black-and-white video camera (if necessary with infrared sensitivity). The software records the position of the animal online with a sample rate of up to 25 frames/s. After identification of the animal in the arena, animal location and orientation with respect to time is determined. In addition, movement velocity and direction, general activity level, and several other behavioural parameters which can include complex behavioural patterns are processed online. Data are presented as graphics and/or tables. Results may also be exported into those programs that are capable of importing graphics (wmf or bmp format) or ASCII-files. VIEWER offers an inexpensive, fast and easy way for analysing simple and complex behaviours of many species of animals in a variety of behavioural situations.

Animals↗

PubMedDate not supplied

Imaging of objects through active electrolocation in Gnathonemus petersii.

The weakly electric fish Gnathonemus petersii detects, localizes, and analyzes objects during active electrolocation even in complete darkness. This enables these fish to lead a nocturnal life and find and identify their prey (small insect larvae) on the ground of their freshwater habitat. During active electrolocation, fish produce a series of brief electric signals, electric organ discharges (EOD), with an electric organ in their tail. Each EOD builds up a stable electric field around the fish, which is distorted only by nearby objects. Field distortions lead to changes of the transepidermal electric current flow at a region of the fish's electroreceptive skin surface called the 'electric image'. Within the electric image, locally perceived EODs can be either altered in amplitude or waveform by an object. Fish measure both parameters to assess object properties, such as the capacitive and resistive components of the object's complex impedance. the object's size and shape, and its distance from the fish. None of these object properties can be evaluated in isolation, but have to be inferred during parallel processing of electric image spatial and qualitative parameters. Two anterior skin regions of G. petersii appear to possess particular properties for special electrolocation tasks and we therefore refer to them as 'foveal' regions. Because of its high electroreceptor density, the electric field geometry around it, and its behavioral use, the 'nasal region' between the nares and the mouth at the head of the fish is suggested to be a fovea for long-range guidance and object detection. We propose that the 'Schnauzenorgan', a long and flexible chin appendix covered densely with electroreceptor organs, is a second electroreceptive fovea associated with a short-range (food) identification system. Together, these two electric foveae constitute an effective prey detection and identification system.

Animals↗

PubMedDate not supplied

Fatal pulmonary failure attributable to viral pneumonia with human herpes virus 6 (HHV6) in a young immunocompetent woman.

Adult respiratory distress syndrome (ARDS) attributable to viral pneumonia is described mainly in immunodeficient persons. ARDS caused by human herpes virus 6 (HHV6) is extremely rare, and to our knowledge only 1 case has been reported in the literature. We present the case of a young woman who developed fatal pulmonary failure most probably attributable to HHV6 pneumonia.

Adult↗